My old system, which specs ar ein my signature, died, i think due to a bad psu. Now i am using my sister's computer. There is a problem, it is running hot, real hot. I am using everest to moniter the temp and it says that the cpu, a 2.6Ghz Celeron 4A is running at an exceptionally cool 35C (95F), but it also says the mobo is running at a scorching 61C (142F). What could be causing this, it is not lagging at all and performance is not slowing down. It just scares me that it is that hot. What could be causing this?

Your Northbridge has a fan or heatsink on it right? If it has a fan, make sure it is cooling properly. Also, you can just get a system fan (120mm) and aim in onto the motherboard to aid in cooling. Motherboards should really run betweem 40-50C, maybe 55C at most. That is pretty warm, it might damage the northbridge controllers wafers if u let that continue. BAD JUJU when silicon wafer transistor series get damaged.... Get a better northbridge cooler for it.

the northbridge has a heatsink, yet it is not hot to the touchm it feels cool if anything. and i cannot find any place on the mobo that feels hot to the touch. maybe there is a problem with the integrated thermometer?

I checked the bios, apparently there is a temp sensor for my cpu, but, one does not exist for my mobo, so i think everest is just making it up. No where in my bios could i find the temp for my mobo, only for my cpu.